The photocatalytic oxidation of nitrite to nitrate over iron-doped TiO2 in aqueous medium under different experimental conditions has been investigated. Specimens of TiO2 doped with different amounts of Fe3+ (between 0.2 and 10 wt.-%) were used; the most photoactive sample was found to be TiO2 doped with 0.5 wt.-%) of iron. The nitrite photooxidation follows; zero-order kinetics for all iron-doped TiO2 samples tested, while for pure TiO2 Langmuir-Hinshelwood kinetics is obtained. The role played by Fe3+ in the photocatalytic processes at the semiconductor-electrolyte interface is discussed. © 1994.